Stable compliance control and its implementation for a 6 DOF manipulator

The authors propose and analyze a method for position-based compliance control with position gain control. It is shown that, for a stiff manipulator, the stable regions of desired compliance are extended by adjusting the internal position feedback gain to a level suitable to the desired compliance. The stable regions in an infinitely stiff environment for various position feedback gains are also described. This position-gain control method was implemented in a compliance-controller consisting of a few microprocessors and a 2-MFLOPS (million floating-point operations per second) floating-point processor. It can control the compliance of an industrial manipulator with six degrees of freedom at a frequency of 500 Hz. As a result of an experiment in which the manipulator under the compliance control was in contact with an infinitely stiff object, it was confirmed that the motion of the manipulator was stable when the compliance parameters were within the theoretically stable region